This invention relates to a process for improving the separation of gases from particle streams, and to an apparatus for carrying out such a process. As used in this specification, "particle streams" shall mean streams in which the particles are conveyed, generally by means of a gas, and wherein the particles constitute an appreciable part of the volume of the stream--as opposed to, for example, the presence of solid particles on a relatively small scale, such as in flue gases and the like. In this specification the term "gas" shall include a vapor.
Where there is a difference between the density of the gas and the density of the particles, the gas has conventionally been separated from the particles by deflecting the stream over a curved surface so that the denser of the two, generally the particles, is compacted or compressed as a result of the centrifugal forces so that the gas is, in effect, squeezed out from between the particles. This is the case with a centrifuge. There are other, more specific, examples which will be referred to below.
In the case of conventional installations, while the great majority of the gas can be removed from the particle stream, there still remains a small amount of the gas trapped in the spaces between the particles. Where the gas is valuable, or where the quantities involved are large, or both, removal of this residual gas could be worthwhile if a way could be found to achieve it economically.
A solution to this problem is proposed in accordance with the invention whereby a substitute gas is introduced into the particle stream in order substantially to replace the carrier gas remaining in the spaces between the particles once the greater part of the carrier gas has been removed from the stream.